The trans-Molecular-Weight-Cut-Off-wise selective separation achieving by amyloid fibril composite nanofiltration membranes

Membranes fabricated by amyloid fibrils can achieve separation of organic matters by size-sieving with normally cis -Molecular-Weight-Cut-Off- wise ( cis -MWCO) selective filtration process. However, size-sieving mechanism revealed that the secondary structures of amyloid fibrils (i.e. local intrinsic pores within an amyloid fibril) was in dormancy during filtration process. By elaborately adjusting the pore size within the fiber network to the range of the local pore size within a single amyloid fibril, the nano-array structures of amyloid fibrils was activated under filtration process. Moreover, the convenient nanochannels built by the consecutive amyloid array facilitated the permeation of some specific organic matters, which should have been rejected by size sieving, leading to the trans -MWCO selective performance. Thus in this paper, two kinds of amyloid fibril composite nanofiltration (AFN) membranes were fabricated by spraying amyloid fibrils onto ultrafiltration substrates. The results showed that both AFN membranes possessed outstanding nanofiltration performances on organic-containing aqueous solution (e.g. oligosaccharides, dyes or pharmaceuticals) with different MWCO points. Noteworthy, AFN membranes fabricated by β-lactoglobulin amyloid fibrils (βLG-AFN) can selectively retain the azo-based compounds (e.g. Chicago sky blue 6B, Congo red), while bovine serum albumin amyloid fibrils covered AFN membranes (BSA-AFN) can selectively block the phenothiazines (e.g. Methylene blue, Chlorpromazine). The optimal separation factor of both βLG-AFN and BSA-AFN membranes can reach up to 37 and 8, respectively. Additionally, the trans -MWCO performance of the AFN membrane may also contribute to the selective recycling of dyes in saline or pharmaceuticals in the patients’ urine. Finally, both antifouling and long-term tests further indicated that the AFN membranes were suitable for sustainable applications in recycling organic contaminants.